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nightsta1ker

Flight dynamics (important issues)

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I think we can wordsmith a bit. They didn't call it a simulation, they called it a game. I didn't see realistic anywhere. The term they used in their marketing is authentic. To me in this context authentic means true. It this a true representation of helicopter flight? I think the general answer is no but it is certainly more than their ARMA titles. Before you can make a flight model a realistic simulation you have have to make sure you have it modeled authentically. There are clearly a few items upside down and backwards here. You get those fixed in the second patch then I think you can get into fine tuning realism and advanced items like vortex ring state. And guys, if you are going to get into things like VRS then you are making more than just a game.

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I will make a video with commentary to help illustrate the core issues. Also Panther and I plan on compiling a list of issues that need to be addressed with references to the Rotorcraft Flying Handbook and other sources.

Great idea!

We respect the feedback and it will be hopefully possible to improve that part of the game with colegues from RTDynamics who provide the flight model code and XML files for Take On Helicopters.

Are you using performance charts of the RL heli counterparts to build the type specific code and the xml files? Or what it is based on? Would such a video (like that one what nightsta1ker is planing) help you, or what type of informations you need?

Edited by EagleEye[GER]

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So after buying and trying the game, I felt that I wasn't doing the right thing. But now reading this topic, It describes exacly what annoyed me all the time (especially the OP in this thread)

The first thing I noticed was the really weird "ground effect" that makes it allmost impossible for me to do a gentle landing. I'm by no means a helicopter expert, but this feels just plain wrong.

The second thing is the misplaced "pivot point" as N1ghtstalker describes nicely.

Together with the unresponsive controls (I might have to tweak my sensitivity/deadzones tho) I end up over-correcting roll wich feels like balancing a broomstick on your forehead...

To be honest, I didnt really enjoy the game yet. Frustrations seem to take the overhand. And trust me i'm one of the most patient guys you can find...

Guess my expectations were too high, or my flight skills are just too bad.

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@Nightstalker

Please don't give up on TOH. It's guys like You and rest of HC family that can really push this game right direction.

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So after buying and trying the game, I felt that I wasn't doing the right thing. But now reading this topic, It describes exacly what annoyed me all the time (especially the OP in this thread)

The first thing I noticed was the really weird "ground effect" that makes it allmost impossible for me to do a gentle landing. I'm by no means a helicopter expert, but this feels just plain wrong.

The second thing is the misplaced "pivot point" as N1ghtstalker describes nicely.

Together with the unresponsive controls (I might have to tweak my sensitivity/deadzones tho) I end up over-correcting roll wich feels like balancing a broomstick on your forehead...

To be honest, I didnt really enjoy the game yet. Frustrations seem to take the overhand. And trust me i'm one of the most patient guys you can find...

Guess my expectations were too high, or my flight skills are just too bad.

+1

Denis

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It's a game. That's all.

And it's a good game (imo). Ok it needs to be updated with better flight dynamics but let BIS work on it. It's not a simulator. Some "simulators" i've flown are not so good (too easy).

I enjoy it: attempting to get a stable hover remember me my first flight on R22!!! I asked my instructor a better heli. He told me: it's not the heli....

Sorry for the OT

AHAHAHHAHAH LOL OLOLOLOL i busted out laughing when i read you asked for a better heli!!

---------- Post added at 12:21 AM ---------- Previous post was at 12:14 AM ----------

So after buying and trying the game, I felt that I wasn't doing the right thing. But now reading this topic, It describes exacly what annoyed me all the time (especially the OP in this thread)

The first thing I noticed was the really weird "ground effect" that makes it allmost impossible for me to do a gentle landing. I'm by no means a helicopter expert, but this feels just plain wrong.

The second thing is the misplaced "pivot point" as N1ghtstalker describes nicely.

Together with the unresponsive controls (I might have to tweak my sensitivity/deadzones tho) I end up over-correcting roll wich feels like balancing a broomstick on your forehead...

To be honest, I didnt really enjoy the game yet. Frustrations seem to take the overhand. And trust me i'm one of the most patient guys you can find...

Guess my expectations were too high, or my flight skills are just too bad.

well sure it may not control like a real helicopter but it's far from uncontrollable. you just have to get used to it. i can tell you any real helicopter pilot that has been playing simulators for a little while can hover and land in these things, they just have to fly it a little differently. so have some more patience and practice, i also do pro bono lessons on multiplayer a lot if you need some tips or guidance.

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@Nightstalker

Please don't give up on TOH. It's guys like You and rest of HC family that can really push this game right direction.

I will be helping Panther put a comprehensive list together of what is modeled incorrectly based on our experience, but at this point I am only helping Panther. He wants to take a more structured approach than I have.

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Recovery is relatively simple, but can cost you alot of altitude when you may not have it (it usually happens in the final stages of an approach to the ground). Lower the nose and go for airspeed, do NOT pull any more collective, in fact, you may need to lower it a bit to help build the flow of smooth clean air over the rotors. When the airspeed starts to climb again, you are in clean air and can pull pitch to recover the descent rate.

If you catch it early, recovery is as simple as pitching the nose forward a bit and ducking out of it. In fully developed VRS you can lose hundreds of feet in just a few seconds. I don't know anything about dual counter-rotating (center mast) helicopters but I would assume the problem would be worse, you have one rotor system right on top of the other. I would imagine one system would get caught in the others vortex sooner and would cause yaw issues as well as an increased sink rate. But what do I know?

Huh, that's a really clear explanation of VRS, I really hope you don't abandon this thread, it's been pretty educational, despite all the weird venom that really doesn't seem warranted in a video game discussion.

I've been able to get into a VRS pretty easily in Black Shark, especially when I was just starting out (Spent a couple weeks learning to actually fly before I even started tackling shooting things at the same time), but I never knew exactly why it was happening when it did, just the conditions that caused it so I could avoid it. Thanks for the lesson, and I'll have to try nosing forward out of it, I usually end up cranking up on the collective and yawing hard left (Habit from spins in IL-2), usually without success. It's rarely recoverable since most of the flying in DCS is pretty low altitude, and a lot of the time with a center mast helicopter, the blades end up intersecting and shattering. DCS is supposed to be a pretty solid sim, so I assume that's close to what would happen in a real KA-50.

And you guys with the arguing, who cares if it's a 3rd party who developed the flight models? They probably read this too, they have a vested interest in continuing to sell their flight dynamics. More importantly, some of us are learning something, and that's kind of weird because I'm on the internet, home of bad memes and porn. Keep it civil? and also :yay:

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Vortex Ring State works like this... You need to have a descent rate of greater than 300 FPM, you need to be below Effective Translational Lift (12-20 knots) and you need to have 20% or more of your engine power applied to driving the rotor system (VRS will NOT happen in an autorotation). It starts with a vibration and some uncrontrolled pitching movement, your descent rate increases, and when you pull collective to stop the descent, it gets worse instead of better. You are sinking into your own rotor wash and all that disturbed air is mucking up the tidy flow of air around your rotors and keeping them from producing lift. As you increase pitch, the problem intensifies and spreads along the blade. You are falling into a black hole.

With little to no forward airspeed and a fast vertical decent I'm surprised this helicopter didn't enter VRS. It must have been right on the edge:

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The three factors I mentioned MUST be present for it to happen, but that does not mean it WILL happen just because those three things are present. On some helicopters, like the Huey and the R22, VRS is actually quite difficult to get into, although it is possible, it's not as likely as some others, like the S300.

Landing with a tail wind often aggravates the phenomenon. A good pilot always knows which way the wind is coming from.

---------- Post added at 05:21 AM ---------- Previous post was at 05:14 AM ----------

I just sent Panther a comprehensive list of everything I have found wrong with the flight dynamics. I did some more test flying tonight and believe I found the source of some issues. I also was pleasantly surprised to find that when I was specifically looking for certain things, they were there. The flight model might not be so bad after all. At this point I feel that there are a couple of bugs that are affecting other aspects of performance so greatly that it made everything seem more "off" than it really is. Once these issues get fixed, the flight dynamics will seem alot more "authentic". And now that I know what the problem really is, I find myself enjoying flying in the game more.

Anyways... pointless drivel... Panther will compile the final list and it will get submitted to the issue tracker for assessment by BI and hopefully we will see some improvement in the second patch.

Time to go enjoy the game. Maybe I will see some of you in multiplayer?

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With little to no forward airspeed and a fast vertical decent I'm surprised this helicopter didn't enter VRS. It must have been right on the edge:

This is a good example of the book world vs the real world. It is my understanding that the 300 FPM rule of thumb for descent rates has it roots from early US Army Aviation practices when they were still training pilots in TH-55's and Hillers. Since the US Army basically wrote the book on standard helicopter practices it has been propagated down into training materials used today ie. The FAA's Rotorcraft Flying Handbook.

I would say not exceeding a 300FPM descent rate in small piston helicopters is very sound advice. In larger helicopters however, it's not that uncommon to see pilots far surpass that descent rate at low gross weights, even with 0 airspeed. You won't see them do this when they are heavy though. I couldn't say with certainty how they get away with this but one theory is it has to do with higher velocity downwash which requires a greater descent rate to catch up to. That doesn't quite make sense to me though because you would think more collective pitch would increase the downwash velocity and sink rate, which would allow you to power out of vortex ring state (and we know this isn't the case). I would ask on the PPRuNe forums if you want an educated response from engineers. I really don't think you can get an experienced response in these forums as all the pilots, including myself have only been the pilot in command of smaller light helicopters.

Edited by LeftSkidLow

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The three factors I mentioned MUST be present for it to happen, but that does not mean it WILL happen just because those three things are present. On some helicopters, like the Huey and the R22, VRS is actually quite difficult to get into, although it is possible, it's not as likely as some others, like the S300.

Landing with a tail wind often aggravates the phenomenon. A good pilot always knows which way the wind is coming from.

---------- Post added at 05:21 AM ---------- Previous post was at 05:14 AM ----------

Time to go enjoy the game. Maybe I will see some of you in multiplayer?

I don't see anyone in multiplayer =(, i'm hosting a game right now.

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Anyone interested in a discussion about what it really takes to get into true VRS, check this thread out. Look for the replies by Nick Lappos, he is or was a test pilot/engineer for Sikorsky.

http://www.pprune.org/rotorheads/116124-vortex-ring-settling-power-merged.html

Here are some excerpts:

I have been in a real case of VRS during some Cat A vertical rejected takeoffs, where I was at about 8 knots forward speed, and at 25 fps ROD, when the bottom fell out, and I was suddenly doing 50 fps when passing through 50 feet (that means 1 second to crunch time, sports fans!) I pulled an armfull of collective at about 5 feet, hit the top collective stops at 1 foot, and whacked the ground at 13.6 feet per second (twice the design sink speed) bounced up and (to make sure I had learned my lesson) hit again at 8 feet per second. To its credit, the S-76 was a lot stronger than advertized, otherwise someone else would be writing this. We wrinkled one stringer in the tail cone.

Theoretical VRS should have been about 25 feet per second.

To calculate the downwash speed (which is the reference for VRS for a particular helo) just take the disk loading in pounds per square foot and multiply by 210, then take the square root. That will give you the feet per second for the 1.0 speed value.

To be conservative, if you take a descent at 50 to 75% of that descent rate, you can avoid VRS.

Here is an example For an R-22, disk area 498 sq ft, GW 1370 lbs, disk loading is 2.75 lbs/sq ft. 2.75 x 210= 577. The square root of 577 is 24 ft/sec, which is the average downwash of an R-22 (24 ft/sec is about 14 knots, or about 1440 ft/min).

This means that the R-22 can't get VRS above about 11 knots forward speed (75% of the downwash velocity), but also that it can't get VRS in a descent less than 700 ft/min (50% of the downwash velocity).

It is somewhat frustrating to know that those who write the guide books for various governments, as well as those who write the tests are schooled in the same pop-aerodynamics course.
Most accidents where a hovering helicopter falls and crashes and VRS is blamed are actually cases of SWP or over pitching, where the hover performance is marginal, and insufficient reserve power (power margin) is available to allow moderate climbs and descents while OGE. The aircraft "falls through" the hover, hits hard (usually with just a bent helicopter and bruised ego) and then someone says "It was VRS." Sometimes the mistaken person is an official accident investigator!

In a helicopter at high MGW, with only slight or no margin between the power needed to HOGE and the power available from the engines, "over pitching" is more likely than in a lightly loaded helicopter where lots of power above hover power is available.

When lightly loaded, there is much extra power available above the hover power, so the lightly loaded helo is much less likely to experience "over pitching" and thus the lightly loaded helo is much less likely to be mistakenly labeled as a VRS accident.

Now the truth: Since true VRS involves the descent of the helicopter into its own downwash, and since in a light helicopter the downwash velocity is quite a bit less than in that same helicopter when heavy, a lightly loaded helicopter needs much less rate of descent to experience true VRS.

Edited by LeftSkidLow

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OT, VRS...

Heli enters VRS at 2:00.

Note this was before I knew what VRS was, the collective was ramped up and up the whole descent and the (correct recovery) pitch forward was not an intentional recovery reaction, but a reaction to the Heli not hitting me or hitting the ground anywhere near me! Don't think you can hear me saying, "I hate it when it does that!"

EDIT: yes, it's RC.

Edited by venquessa

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Sorry md500enthusiast,I wound up on the phone with my wife instead of getting online. Tonight I will be online.

Leftskidlow is right about pprune, there is alot of knowledge there and you are going to be able to get better answers from pilots with tens of thousands of hours. There are some living legends that frequent that forum. And it is very true that the "book" answer is not neccessarily the right answer. Even the engineers are still trying to figure out how some of the physics work. Helicopters are strange, temperamental beasts.

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I will be helping Panther put a comprehensive list together of what is modeled incorrectly based on our experience, but at this point I am only helping Panther. He wants to take a more structured approach than I have.

Good idea, but it may be a moot point. We've put hundreds of hours into feedback already with little result. Furthermore, BIS attributes the FM issues to a third party and your efforts may not have the desired end-state. (Yup, I know I'm flogging a dead horse here, but it's important to stay active I think)

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Good idea, but it may be a moot point. We've put hundreds of hours into feedback already with little result. Furthermore, BIS attributes the FM issues to a third party and your efforts may not have the desired end-state. (Yup, I know I'm flogging a dead horse here, but it's important to stay active I think)

Do you really read what our developers are saying? I am not sure.

We welcome solid feedback and we are always trying to improve our products based on good and productive cooperation with our valuable user communities (and really there is no need to use strategy of broken record with us to achieve best results, it is much more useful to provide really specific feedback).

We really like and play this game a lot in our studios but that does not mean we are not prepared to improve it further.

Yes, it is correct the flight model is licensed from a 3rd party which makes our iterative development practice a bit harder this case.

The game is just released, if you are interested you can find out what our current support plans are.

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Good idea, but it may be a moot point. We've put hundreds of hours into feedback already with little result. Furthermore, BIS attributes the FM issues to a third party and your efforts may not have the desired end-state. (Yup, I know I'm flogging a dead horse here, but it's important to stay active I think)

Chris,

As I said before, I'm just helping Panther at this point. What the end state happens to be is out of my hands. I'm absolutely done beating this "dead horse" as you put it. I was just posting an update.

Thanks for the post Maruk, always nice to hear from the CEO regarding customer support. We are behind your company 100%!

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Thanks for the post Maruk, always nice to hear from the CEO regarding customer support. We are behind your company 100%!

Indeed. I really can't bring myself to play the game anymore, but I really, really want to see it go to the next level and will help if I can.

Edit: The software as it is right now is an absolutely fantastic proof of concept. I don't want to take anything away from the hard work that was put into everything that was done well. I just feel like it needs an extra 'push' to go get to where it should be.

Edited by Chris CDN

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Sorry md500enthusiast,I wound up on the phone with my wife instead of getting online. Tonight I will be online.

.

it's ok nightstalker, I FORGIVE YOU!! :D :cool: :p :yay:

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Maruk,

My Hovercontrol guys are working up their review and suggestions. We should have something together shortly.

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Maruk,

My Hovercontrol guys are working up their review and suggestions. We should have something together shortly.

Whats the status on that? I guess, you wanted to do the test again with Patch1?

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Patch 1 has nothing to do with the flight modeling. I think that is scheduled for patch 2 depending on the difficulty involved.

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you can change it yourself ;):

1.backup the original file first!!

2.unpack the air_us_h.pbo file located in the folder addons with Extractpbo (put dpbo.dll in the same folder)

3.in the extracted folder go to air_us_h > h_sim > air_us_h the last sub-folder is the folder you need repack to create the new air_us_h.pbo file (i do it with cpbo)

4.in this folder you have the 3 more sub folders medium, heavy and light into each folder you have a .xml file ej: Light-GenHeli600-DesktopSim.xml this is the config file to the light i edit this file with the notepad

5.repack and test (repack the sulfolder air_us_h> h_sim > air_us_h instead the entire extracted folder)

note: locate the tools folder in the desktop and run as administrator (win 7 and vista)

personally i've found the default ( ib= 1200 ) too low in the medium, with 1800 ~ 2200 improve the control authority and almost cancel the roll tendency with collective input due to the tail rotor high position, set the yaw control damper to 0 ~ 0.5 to get yaw torque effect

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